Car crash collsion

Question:
A 480kg car moving at 14.4m/s hits from behind another car moving at 13.3m/s in the same direction. If the second car has a mass of 570kg and a new speed of 17.9m/s what is the velocity of the first car after collision?

Since there is a velocity for one car after the collision and the question asks for the other car's velocity after the collison this collision must be elastic.
Thus
m1v1 + m2v2 = m1v1f + m2v2f
480*14.4 + 570*13.3 = 480v1f + 570*17.9
14493N = 480v1f + 10203N
4290N = 480v1f
8.94m/s = v1f